When it comes to keeping a 1990s Porsche mountain bike performing well, it's all about the elastomers. The Porsche Bike S, Bike FS and Bike ST had front shocks built with an internal spring and with as many as nine small, cylindrical elastomers (see photo below) on each side. But what is an elastomer anyway?
An elastomer is a polymer with viscoelasticity (having both viscosity and elasticity) and very weak inter-molecular forces, generally having high failure strain compared with other materials. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber.
Wikipedia says:
An elastomer is a polymer with viscoelasticity (having both viscosity and elasticity) and very weak inter-molecular forces, generally having high failure strain compared with other materials. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber.
The two things to understand from this definition is Porsche/Votec used the elastomer inherent elasticity for front shock vibration dampening and the other is the high strain failure.
Back in the 1990s this is how mountain bike shocks were made. Cutting edge technology. Today, no one makes shocks like this anymore. Why? High failure rate due to strain - and more importantly, time.
Mix strain and time together and all of these nearly 20 year old Porsche bicycles have a pending elastomer failure to deal with. The clock is ticking. The elastic polymer starts to dry out and lose its elasticity. Then they crack and ultimately break apart leaving a mess inside the shock housing and making the bike unrideable. This can happen slowly over time, or in some cases the shocks just collapse all at once.
Even though the Porsche Bike S and Bike FS can be frequently found on both the US and German eBay sites, these bikes were a limited run and really aren't that many around. Porsche enthusiasts and investors, rather than cyclists bought these up. So today it is easy to find a Bike S or Bike FS in pretty good condition. Albeit with elastomers about to fail.
Although that seems like a bad deal to most, that can also create an opportunity for others. I bought a Bike S from a pawn shop in Florida off eBay for only $600 because the seller said "the bike was unrideable because the front forks were broken and no parts are available." He offered it for sale as a display piece. I knew exactly what was wrong with it. Spending $100 on new elastomers and some garage time and now I have a great Bike S in excellent shape - even rode it 100 miles in one day last fall. Considering you'll find 1990s Porsche bikes ranging from $1,500 to $3,000 on eBay, $700 was not a bad deal.
How can you do a Porsche shock rebuild yourself you ask? Well, it's not that hard if you have the parts and know what you're doing.
For starters, it's easier if you order the elastomers pre made and precut to fit. The online bicycle elastomer sales website www.suspensionforkparts.com is the best/only place in the entire world to buy these specific elastomers. Get the kit that includes the lube - very important.
As for knowledge, this Porsche bike blog covers what to do. You may have to dig through the site a little or you can post a comment and just ask me. I love working on these bikes AND freely sharing what I've learned.
So, if you want to buy an old Porsche bike, or already have one, and are afraid of the pending shock failure, don't be. This site can help you rebuild your bike into original and amazing condition - which will last for another 20 years.
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